Flexible fluid level sensor with improved measurement capability

ABSTRACT

A capacitive fluid sensor is provided having a substrate having upper and lower ends and conductive members supported by the substrate. The conductive members are provided between the upper and lower ends of the substrate. The conductive members include an upper end conductive member, a lower end conductive member, and at least one included conductive member which is positioned between the upper and lower end conductive members. Each conductive member is separated from every other one of the members, thereby providing that each member has distinct upper and lower ends and acts as an independent sensor. At least one pair of proximally positioned members are positioned relative to each other such that the distinct lower end of one of the pair of conductive members is positioned closer to the lower end of the substrate than is the distinct upper end of the other one of the pair of conductive members.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/705,375, filed Dec. 5, 2012, which application is incorporated hereinby reference in its entirety.

BACKGROUND OF THE PRESENT DISCLOSURE

The Present Disclosure relates generally to fluid sensors, and, inparticular, to sensors that have a flexible body for application tofluid containers of varying configurations, as well as sensors that haveimproved sensor capabilities.

Fluid sensors are used in a variety of applications. Their usage in themedical arts has grown, and sensors are used in association withbiopumps that remove a certain volume of fluid from a body location,with containers such as beakers, columns and drip bags, to measurepredetermined levels of fluid for infusion into the body. Otherapplications are known, and many of these fluid containers haveirregularly-shaped exterior configurations, making it difficult to readthe measurements scribed on their sides. Optical measurement indicia,such as graduated lines, are hard to difficult to read in an automatedmanner, and are not conducive to fast timing diagnostic and otherprocedures. Hence, fluid sensors were developed that may be attached tocontainers and which can provide readout signals that may be displayed,or otherwise read, by a monitoring device.

Such a fluid sensor is described in U.S. Pat. No. 6,490,920, issued 10Dec. 2002, the content of which is hereby incorporated herein in itsentirety. The sensor described in the '920 Patent utilizes a flexiblesubstrate that supports a series of conductive members disposed on asurface of the substrate and are arranged to form a single sensor withmultiple, interacting members, more in the form of appendages thatextend in opposite directions from a baseline of each such member. Theseappendages are interlaced with each other so that they appear as aseries of fingers that extend into gaps between adjacent fingers of anopposite member. As such, each member of the sensor of the '920 Patentconstitutes one single and elongated sensor member. The large length ofthis sensor reduces its ability to accurately, at very small tolerancesmeasure fluid levels. Although it is suitable for a gross measurement,it is difficult to obtain very fine tolerance fluid level readings. ThePresent Disclosure is therefore directed to an improved fluid sensorbetter suited for capacitively measuring fluid levels in containers, andparticularly irregularly shaped containers.

SUMMARY OF THE PRESENT DISCLOSURE

Accordingly, there is provided an improved fluid level sensor that has abetter tolerance, resulting in finer measurements for exteriormeasurement of fluids held within a container.

In accordance with an embodiment as described in the followingdisclosure, a sensor comprises a flexible substrate, provided as anelongated strip. A plurality of conductive portions, members orelectrodes are disclosed, each of which has a plate-like configurationwhich is supported on the substrate. The conductive members are arrangedin an array, each array containing a desired number of distinctconductive members. The members are separated from each other by aplurality of intervening spaces and each such conductive member has aconductive trace connected to it, which extends from the conductivemember longitudinally along the substrate to a connecting end of thesubstrate where it joins a contact pad. These contact pads providepoints of connection for the sensor so that the sensor may be insertedinto a connector and connected to circuitry of a readout or processoroperatively connected to a display means. The substrate includesmultiple layers with a thin polyester layer supporting the conductivemembers thereon, which may easily be applied thereto by way of printingor the like. A cover layer of polyester or other suitable material maybe provided to seal the conductive members in place, and a layer ofpressure-sensitive adhesive may be applied to a mounting side of thesubstrate.

The conductive members are further configured such that all but two ofthe members, those lying at the opposing ends of the array, are of thesame configuration. In other words, the conductive members that areincluded between the second, and the second to last, conductive member(or “penultimate” members) are substantially identical in configuration.In one embodiment, the conductive members may include four-sided membersthat are oriented on the substrate at an angle respect to a longitudinalaxis of the substrate, such that the intervening spaces separating theconductive member extend at angle to the longitudinal axis and, andintersect the longitudinal axis at an angle thereto. In this manner,when a point of reference is taken that is normal to the substratelongitudinal axis, the conductive members, in effect, overlie each otherand any line drawn within any of these included conductive members thatis normal to the substrate longitudinal axis and within the endboundaries of conductive members will contact two adjacent conductivemembers.

As the conductive members are separated by their associated interveningspaces, each such conductive member becomes a single sensor in thearray, having a given measurement tolerance between the ends, in alengthwise direction of each conductive member. These single sensors maybe made with a given tolerance, such as 5%, and the use of multiplesensors, each with a 5% tolerance within its boundaries will provide atolerance of 0.05% over the entire length of the sensor.

In another embodiment of the Present Disclosure, the conductive membershave a configuration similar to that of a chevron, so that theintervening spaces between adjacent conductive members are angled in anon-linear manner, meaning that they extend in different directions asbetween adjacent conductive members, so that there is a similar overlapof adjacent sensors occurs in a normal direction as mentioned above withrespect to the first embodiment. In the embodiment described previously,the four sided figures may be parallelograms and in yet anotherembodiment, a singe sensor or multiple sensors may be at least partiallysurrounded by a lattice-type arrangement of conductive traces.Conductive traces extend from the conductive members to a connecting endof the sensors and extend along the outside edges of the conductivemembers. They may be typically divided into two groups, one with anequal number of traces and the other with an uneven number of traces.

In yet another embodiment, the array of sensors, or in certaininstances, a single sensor, may be surrounded by a ground grid that maybe considered as a lattice, which includes a plurality of conductivetraces arranged in a diagonally intersecting fashion. This latticenetwork defines a ground shield that surrounds the conductive member(s).The ground shield is connected to the connecting end of the sensor byway or one or more conductive traces for connection to a processor.

These and other objects, features and advantages of the PresentDisclosure will be clearly understood through a consideration of thefollowing detailed description.

BRIEF DESCRIPTION OF THE FIGURES

The organization and manner of the structure and operation of thePresent Disclosure, together with further objects and advantagesthereof, may best be understood by reference to the following DetailedDescription, taken in connection with the accompanying Figures, whereinlike reference numerals identify like elements, and in which:

FIG. 1 is a perspective view of an irregularly-shaped fluid containerwith a fluid sensor constructed in accordance with the principles of thePresent Disclosure in place on an exterior surface thereof;

FIG. 2 is a top plan view of one embodiment of the fluid sensor of FIG.1, which utilizes a plurality of four-sided conductive members arrangedin an angular orientation along a flexible substrate;

FIG. 2A is an enlarged detail view of a portion of FIG. 2, showing theoverlapping array of conductive members within the sensor;

FIG. 2B is a sectional view taken of a portion of the sensor at “B” ofFIG. 2;

FIG. 3 is a top plan view of a second embodiment of the fluid sensor ofFIG. 1, which utilizes a series of chevron-shaped conductive membersarranged along a longitudinal axis of a flexible substrate;

FIG. 4 is a top plan view of yet another embodiment of the fluid sensorof FIG. 1, which utilizes a single conductive member surrounded by alattice, or angled grid, of conductive traces which are interconnectedto form a ground shield; and

FIG. 5 is a top plan view of another embodiment of the fluid sensor ofFIG. 1, utilizing a ground grid as a shield in the manner of theembodiment of FIG. 4, but which utilizes an array of conductive membersas its sensor.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

While the Present Disclosure may be susceptible to embodiment indifferent forms, there is shown in the Figures, and will be describedherein in detail, specific embodiments, with the understanding that thePresent Disclosure is to be considered an exemplification of theprinciples of the Present Disclosure, and is not intended to limit thePresent Disclosure to that as illustrated.

As such, references to a feature or aspect are intended to describe afeature or aspect of an example of the Present Disclosure, not to implythat every embodiment thereof must have the described feature or aspect.Furthermore, it should be noted that the description illustrates anumber of features. While certain features have been combined togetherto illustrate potential system designs, those features may also be usedin other combinations not expressly disclosed. Thus, the depictedcombinations are not intended to be limiting, unless otherwise noted.

In the embodiments illustrated in the Figures, representations ofdirections such as up, down, left, right, front and rear, used forexplaining the structure and movement of the various elements of thePresent Disclosure, are not absolute, but relative. Theserepresentations are appropriate when the elements are in the positionshown in the Figures. If the description of the position of the elementschanges, however, these representations are to be changed accordingly.

FIG. 1 is a perspective view of a fluid container 20 and a fluid sensor22 constructed in accordance with the principles of the PresentDisclosure. As can be seen, the fluid container 20 takes the form of abeaker 24 having a wide base portion 25 that narrows in diameter as itrises vertically to a narrow neck portion 26 before is expands radiallyoutwardly to form a lip portion 27. The container 20 is made from glass,plastic or another non-conductive material. Typically, such containersare provided in a “graduated” form; that is, it will have a series ofhorizontal level lines that are formed on its sidewall either by etchingor printing. One may determine the level of a fluid within the container20 by looking at the side of container. Such a reading is accomplishedonly by viewing the container 20 and such a determination requires thatthe container be placed on a level surface. Moreover, it is difficult toautomate a visual reading of the fluid level. Accordingly, the PresentDisclosure is directed to a fluid level sensor that is prone to easyautomated readings and is capable of being utilized with a variety ofirregularly-shaped fluid containers.

FIG. 2 illustrates, in plan view, a capacitive fluid level sensor 22 ofthe Present Disclosure. As illustrated, the sensor 22 is formed as anelongated strip 30 and has a non-conductive, dielectric substrate 32that serves as a base portion of the sensor 22. The substrate 32 has twoopposing sides, or surfaces 33, 34, one of which, 33, is a mounting sidethat is intended to be attached directly to the exterior of the fluidcontainer 20. The substrate 32 is preferably formed from an inexpensiveflexible dielectric material, such as polyester. A polyester substratealso permits the conductive members to be easily applied to thesubstrate 32, such as by screen printing or other suitable means.

The sensor 22, as best shown in the sectional view of FIG. 2B, mayfurther include a cover layer 35 applied to the upper surface 34 of thesubstrate 32, and serves to isolate the conductive members 50 betweentwo dielectric layers. A layer 36 of a pressure sensitive adhesive maybe applied to the bottom, or mounting, surface 33 of the substrate 32 sothat the sensor 22 may be applied to a container 20. In particular, theflexible nature of the substrate 22 permits it to be applied toirregularly shaped containers such as the beaker. Alternatively,intravenous plastic bags (not shown) or other type containers may alsobe used. A non-conductive backing member 37 may be provided at theconnecting end 38 of the substrate 32, where the width is sufficientlynarrowed to form a sensor insertion end that contains a plurality ofcontact pads 40 and which may be inserted into a receiving slot 41 of areceptacle connector 42, may be provided as part of an overall fluidlevel detection system that may be plugged into a computer or processormounted on a small circuit board 44 by way of an appropriate connectionmeans, such as the USB cable 43 shown. The adhesive layer 36 permits thesubstrate 32 to be applied to the exterior surface of a container 20 andespecially an irregularly-shaped container such as the beaker 24 shownin FIG. 1.

In order to determine the fluid level, the sensor is provided with aplurality of conductive members, or electrodes, generally, 50, andspecifically in FIG. 2, 50 a-50 j are arranged in a given pattern, orarray 51. In each such arrangement, the conductive members 50 areseparated from each other by intervening spaces 52. Further, as shown ina first embodiment as illustrated in FIG. 2, the conductive members 50include a plurality of four-sided members 53. The conductive members 50in this embodiment are of two types. The first type of conductivemembers 50 a, 50 j are those found at the opposite ends 54 of the array51 and shall be referred to herein as “end” conductive members, whilethe second type of conductive members 50 b-50 i are those members thatare included between the end members, and shall be referred to herein as“included” conductive members. The conductive members 50 b and 50 i thatmake up the ends of the included members may be referred to as“penultimate” conductive members. The included conductive memberspreferably are all identical to each other and more preferably they areall parallelograms having perimeters, or boundaries, made up of opposingends 56 a, 56 b and opposing sides 57 a, 57 b that are joined togetherat respective inner and outer corners 58, 59. The resulting four-sidedconfigurations of the conductive members are more diamond orrhombus-like shapes rather than rectangles.

It is desirable to have the included conductive members 50 b-50 iarranged so that their intervening spaces 53 intersect the chosenlongitudinal axis LA of the substrate 32, or sensor 22, at an angle andthe angle is chosen so that preferably, as illustrated in FIG. 2A theinner corners 58 are spaced apart from each other, or in other words,Lines AA and BB drawn through the inner corners 58 and normal to thelongitudinal axis LA are not coincident, but rather, are spaced apart.Similarly, any line drawn within the body of an included conductivemember 50 b-50 i, in a direction normal to the substrate longitudinalaxis LA will contact, or intersect two adjacent conductive members. Inthis fashion, the conductive members 50 may be considered as overlappingeach other, when viewed from a side edge of the substrate 32, or inother words, the intervening spaces 53 provide no clear path thatintersects the longitudinal axis LA in a direction normal to the axisLA. This permits the capacitive measurement aspect to work along theentire array 51 of conductive members 50 without any interruption as mayoccur were the intervening spaces to be arranged normal to thelongitudinal axis LA. The sensor 22 relies upon an inherent, parasiticcapacitance to provide its level measurement function in that eachconductive member 50 acts as a single plate of a capacitor with thesurrounding material and circuitry coupled to ground as the other plate,in a manner different from sensors in the art that use a pair of platesfor each conductive member. The conductive members 50 may be formed byscreen printing a silver-based or other conductive ink on the substrate32 or by stamping them out of a thin metal sheet stock and embeddingthem, in the substrate 32, or any other suitable manner.

The angled orientation of the conductive members 50 not only providesthe overlap mentioned above but also increases the accuracy of the levelmeasurement. The accuracy obtained within each conductive member mayhave a tolerance or 5% or the like, but that is within the length “L” ofthe conductive member, namely, the area that lies between imaginarylines CC drawn normal to the outer corners of the included conductivemembers 50 b-50 i. By containing the tolerance within each conductivemember, the overall level is reduced by the tolerance of each conductivemember divided by the total number of conductive members. In thismanner, the measurement accuracy of the sensor is greatly increased. Aplurality of conductive traces 60 are arranged on the substrate and areprovided to connect the conductive members 50 with contact pads at theconnecting end of the sensor. As shown the traces 60 may be arranged intwo groups and they can extend, as illustrated along both sides of thearray of conductive members. The traces may be arranged in even groupsor one group with an even number of traces and the other group with anodd number of traces. Alternatively, the traces may be arranged in theirown layer underneath the conductive members and insulated therefrom.

FIG. 3 illustrates another embodiment of a sensor 80 of the PresentDisclosure in which the conductive members 82 have five and six-sidedconfigurations. The conductive members 82 a-j include end members 82 a,82 j, each of which includes a five-sided figure and a series ofincluded conductive members 82 b-82 i, each of which includes asix-sided figure and each of which are preferably identical to eachother. In this embodiment, the conductive members 82 are aligned along alongitudinal axis of the substrate and are spaced apart from each otherby intervening spaces 84. The spaces 84 are angled as in the firstembodiment but in this embodiment they extend in two differentdirections, thereby giving the conductive members 82, at least theincluded conductive members 82 b-82 i chevron-like configurations. Eachsuch included conductive member 82 b-82 i has a chevron configurationwith a top portion 85 that is nested within a valley portion of anadjacent conductive member. As such, adjacent conductive members overlapeach other when viewed from the side of the substrate in a directionnormal to the longitudinal axis of the substrate. Conductive traces 87are provided to connect the conductive members 80 to contact pads on theconnecting end of the sensor 80.

Another embodiment of a sensor 90 is illustrated in FIG. 4, whichincludes a substrate 91, and an elongated, four-sided conductive member92 that is surrounded by a conductive grid, or lattice 93. The grid 93is composed of a plurality of conductive traces 94 that are organized inan angular or diagonally interconnected relationship defining a networkof openings 95 between the traces 94. The grid 93 is typically connectedto a ground contact pad on the connecting end of the sensor 90 so thatthe grid 93 may act as the second plate of a capacitive pair with theconductive member 92. FIG. 5 illustrates another variant of a sensor 100that utilizes the array of chevron-shaped conductive members 102 shownearlier that are aligned along a longitudinal axis and which areseparated by intervening spaces 104. A conductive grid 105 is providedthat encircles the array of conductive members 102 and the grid 105 hasa lattice type configuration of a plurality of interconnected orintersecting traces 106, which define a series of enclosed openings.This grid 105 is connected to a ground terminal and acts as a secondplate to the conductive members 102 in order to provide capacitiveinteraction between the two. Connecting traces 108 are provided tointerconnect each conductive member 102 and the grid 105 to contact padsat a connecting end of the sensor. These connecting traces 108 run in aseparate layer from the conductive members 102 and are insulatedtherefrom.

While a preferred embodiment of the Present Disclosure is shown anddescribed, it is envisioned that those skilled in the art may devisevarious modifications without departing from the spirit and scope of theforegoing Description and the appended Claims.

What is claimed is:
 1. A capacitive fluid level sensor assembly, thecapacitive fluid level sensor assembly comprising: a substrate havingupper and lower ends; and a plurality of conductive members supported bythe substrate, the plurality of conductive members being providedbetween the upper and lower ends of the substrate, wherein the pluralityof conductive members includes an upper end conductive member which ismost proximate to the upper end of the substrate, a lower end conductivemember which is most proximate to the lower end of the substrate, and atleast one included conductive member which is positioned between theupper and lower end conductive members, wherein each conductive memberis separated from every other one of the conductive members, therebyproviding that each conductive member has distinct upper and lower endsand acts as an independent sensor, wherein at least one pair ofproximally positioned conductive members are positioned relative to eachother such that the distinct lower end of one of the pair of conductivemembers is positioned closer to the lower end of the substrate than isthe distinct upper end of the other one of the pair of conductivemembers.
 2. The capacitive fluid level sensor assembly as defined inclaim 1, wherein the substrate is configured to be positioned alongsidea wall of a vessel.
 3. The capacitive fluid level sensor assembly asdefined in claim 2, wherein the substrate is configured to be positionedalongside an exterior wall of the vessel.
 4. The capacitive fluid levelsensor assembly as defined in claim 2, wherein a layer ofpressure-sensitive adhesive is applied to at least a portion of amounting side of the substrate.
 5. The capacitive fluid level sensorassembly as defined in claim 1, wherein the substrate is formed from aflexible material.
 6. The capacitive fluid level sensor assembly asdefined in claim 1, wherein the substrate is formed from a dielectricmaterial.
 7. The capacitive fluid level sensor assembly as defined inclaim 1, wherein a cover layer seals the plurality of conductive membersto the substrate.
 8. The capacitive fluid level sensor assembly asdefined in claim 1, wherein the substrate defines an axis which extendsfrom the upper end thereof to the lower end thereof, and wherein anyimaginary line drawn normal to the axis which intersects an includedconductive member also intersects at least one of the other conductivemembers.
 9. The capacitive fluid level sensor assembly as defined inclaim 1, wherein the substrate has an insertion portion which isconfigured to be inserted into a receiving slot of a receptacleconnector.
 10. The capacitive fluid level sensor assembly as defined inclaim 9, wherein the insertion portion of the substrate contains aplurality of contact pads which are electrically connected to theplurality of conductive members.
 11. The capacitive fluid level sensorassembly as defined in claim 9, wherein the insertion portion of thesubstrate is provided at one of the upper and lower ends of thesubstrate.
 12. The capacitive fluid level sensor assembly as defined inclaim 1, wherein an intervening space is defined between adjacentconductive members.
 13. The capacitive fluid level sensor assembly asdefined in claim 12, wherein the substrate spans the intervening space.14. The capacitive fluid level sensor assembly as defined in claim 12,wherein the intervening space intersects a longitudinal axis of thesubstrate at an angle.
 15. The capacitive fluid level sensor assembly asdefined in claim 12, wherein the intervening space extends in twodifferent directions.
 16. The capacitive fluid level sensor assembly asdefined in claim 1, wherein the distinct lower end of a lowermostincluded conductive member is positioned closer to the lower end of thesubstrate than is the distinct upper end of the lower end conductivemember.
 17. The capacitive fluid level sensor assembly as defined inclaim 16, wherein the distinct lower end of the lowermost includedconductive member is at least one point.
 18. The capacitive fluid levelsensor assembly as defined in claim 16, wherein the distinct upper endof the lower end conductive member is at least one point.
 19. Thecapacitive fluid level sensor assembly as defined in claim 1, whereinthe distinct upper end of an uppermost included conductive member ispositioned closer to the upper end of the substrate than is the distinctlower end of the upper end conductive member.
 20. The capacitive fluidlevel sensor assembly as defined in claim 19, wherein the distinct upperend of the uppermost included conductive member is at least one point.21. The capacitive fluid level sensor assembly as defined in claim 19,wherein the distinct lower end of the upper end conductive member is atleast one point.
 22. The capacitive fluid level sensor assembly asdefined in claim 1, wherein each conductive member has a plate-likeconfiguration.
 23. The capacitive fluid level sensor assembly as definedin claim 1, wherein the plurality of conductive members are provided inan array between the upper and lower ends of the substrate.
 24. Thecapacitive fluid level sensor assembly as defined in claim 1, whereineach of the upper end conductive member and the at least one includedconductive member have sides which are planar to one another.
 25. Thecapacitive fluid level sensor assembly as defined in claim 1, whereineach of the lower end conductive member and the at least one includedconductive member have sides which are planar to one another.
 26. Thecapacitive fluid level sensor assembly as defined in claim 1, whereineach of the lower end conductive member and the upper end conductivemember have sides which are planar to one another.
 27. The capacitivefluid level sensor assembly as defined in claim 1, wherein the at leastone included conductive member comprises a plurality of includedconductive members, and wherein at least one of the included conductivemembers have sides which are planar with sides of the lower endconductive member.
 28. The capacitive fluid level sensor assembly asdefined in claim 27, wherein all of the included conductive members havesides which are planar with sides of the lower end conductive member.29. The capacitive fluid level sensor assembly as defined in claim 1,wherein the at least one included conductive member comprises aplurality of included conductive members, and wherein at least one ofthe included conductive members have sides which are planar with sidesof the upper end conductive member.
 30. The capacitive fluid levelsensor assembly as defined in claim 29, wherein all of the includedconductive members have sides which are planar with sides of the upperend conductive member.
 31. The capacitive fluid level sensor assembly asdefined in claim 1, wherein the upper end conductive member has aconfiguration which is different from a configuration of the at leastone included conductive member.
 32. The capacitive fluid level sensorassembly as defined in claim 1, wherein the lower end conductive memberhas a configuration which is different from a configuration of the atleast one included conductive member.
 33. The capacitive fluid levelsensor assembly as defined in claim 1, wherein the upper end conductivemember has a configuration which is different from a configuration ofthe lower end conductive member.
 34. The capacitive fluid level sensorassembly as defined in claim 1, wherein the at least one includedconductive member is four-sided.
 35. The capacitive fluid level sensorassembly as defined in claim 34, wherein the at least one includedconductive member is in the form of a parallelogram.
 36. The capacitivefluid level sensor assembly as defined in claim 1, wherein the at leastone included conductive member is six-sided.
 37. The capacitive fluidlevel sensor assembly as defined in claim 36, wherein the at least oneincluded conductive member is in the form of a chevron.
 38. Thecapacitive fluid level sensor assembly as defined in claim 1, whereineach conductive member is electrically connected to circuitry of areadout or processor.
 39. The capacitive fluid level sensor assembly asdefined in claim 1, wherein the at least one pair of proximallypositioned conductive members includes the upper end conductive memberand an uppermost included conductive member.
 40. The capacitive fluidlevel sensor assembly as defined in claim 1, wherein the at least onepair of proximally positioned conductive members includes the lower endconductive member and a lowermost included conductive member.
 41. Thecapacitive fluid level sensor assembly as defined in claim 1, whereinthe at least one pair of proximally positioned conductive membersincludes two included conductive members.